TV Typewriter

The TV Typewriter was a video terminal that could display 2 pages of 16 lines of 32 upper case characters on a standard television set. The Don Lancaster design appeared on the cover of Radio-Electronics magazine in September 1973.[1] The magazine included a 6 page description of the design but readers could send off for a 16 page package of construction details. Radio-Electronics sold thousands of copies for $2.00 each. The TV Typewriter is considered a milestone in the home computer revolution along with the Mark-8 and Altair 8800 computers.[2][3]

Sometimes the term was used generically for any interactive computer display on a screen; until CRT displays were developed, the teleprinter was the standard output medium.

Contents

Don Lancaster was an engineer at Goodyear Aerospace designing a high resolution video display for the military. Don was also a prolific author of hobbyist projects for Popular Electronics and Radio-Electronics magazines. The video project gave Don the inspiration for his most influential project, a low cost video terminal known as the TV Typewriter. The design used TTL digital logic and shift register memory. (Microprocessors and RAM were new and very expensive.) With professional terminals costing over $1000 this $120 kit looked like a bargain. Southwest Technical Products sold the set of bare circuit boards for $27 and the eight major integrated circuits for $49.50. The hobbyist had to acquire the rest of the components on their own.

In the November issue, the editors apologized for the delays in shipping the TV Typewriter booklets to the thousands of readers that ordered them. They also listed electronics parts sources for the difficult to find components. Don Lancaster also answered a series of reader questions and gave ideas for additional functions and uses for the TV Typewriter.[4] The December issue had a page of corrections for the TV Typewriter booklet.[5] Both of the notices were included in later printings of the booklet.

The compact design and complex circuitry made the TV Typewriter a challenging project for hobbyists. But many finished the project and some even connected it to their Intel 8008 based computers. The April 1975 issue of the Micro-8 Newsletter has 6 pages of user modifications and interface designs to connect the TV Typewriter to Mark-8 or SCELBI computers.[6] The original TV Typewriter design did not include a serial interface, modem connection, or offline data storage on cassette tape. Don Lancaster wrote about these in the September 1975 issue of BYTE magazine and his TV Typewriter Cookbook. A serial interface board designed by Roger Smith was published in the February 1975 issue of Radio Electronics.[7]

Today keyboards are readily available, inexpensive and have a standard interface. In 1973, new keyboards were only available to computer and terminal manufacturers. Surplus keyboards were available to hobbyists but they often produced codes other than ASCII, such as baudot or EBCDIC. The TV Typewriter project and kit did not include a keyboard. The unit on the September cover shows a keyboard project Don Lancaster did in the February 1973 issue.[8] This project involved hand crafting 55 key-switches including fabricating the springs for each key-switch. Most hobbyists chose to use a surplus keyboard and modified it to produce ASCII codes. Don Lancaster's prototype TV Typewriter which is now on display at the Computer History Museum has a surplus keyboard with an ASCII encoder circuit that was published in the February 1974 issue of Radio-Electronics.[9] The plans for this encoder were also included in the TV Typewriter booklet

Popular Electronics (April 1974) featured a complete keyboard kit designed by Don Lancaster and available from Southwest Technical Products for $39.50.[10] The first version used simple RTL ICs to decode the key matrix. The design was soon improved to use a full featured keyboard encoder IC.

The original TV Typewriter was difficult to assemble and some of the ICs were going out of production so Southwest Technical Products decided to redesign the kit. The replacement was featured in Radio Electronics as the TV Typewriter II. This time readers did not have to order a set of plans, since the complete design was published in 6 issues starting in February 1975.

Daniel Meyer of SWTPC enlisted Ed Colle, an engineer who had worked at Datapoint on terminal design, to design the new TV Typewriter. The SWTPC CT-1024 Terminal displayed 32 characters by 16 lines without scrolling. It used common TTL parts and 2102 static RAMS. The boards were laid out with very loose part spacing and wide traces to make it easy to assemble. A complete set of option boards were offered including a serial interface. The keyboard was based on Don Lancaster’s design. The rest of the terminal was done by Ed Colle.

The design was finished by late 1974 and the kits were ready for sale by December 1974. The first advertisement for the CT-1024 appeared in the January 1975 issue of Popular Electronics on the page facing the Altair 8800 computer article.[11] The CT-1024 was very successful because a complete kit with options cost only $275. It was replaced in 1977 by the improved CT-64 that offered scrolling and 64 characters per line of upper and lower case.

By 1975 Don Lancaster had written over 100 articles in magazines such as Popular Electronics and Radio-Electronics. He had also written a digital design book titled the RTL Cookbook in 1968. Resistor-transistor logic (RTL) was an early IC technology that was replaced by TTL, so in 1974 he published the TTL Cookbook. This book was in print for 20 years and sold a million copies.

The original TV Typewriter was designed before low cost RAM was available and the design was soon obsolete. Don had made many design improvements and published them as the TV Typewriter Cookbook in 1976. Portions had been serialized in the first issues of Byte magazine. The book was a guide on how to design a video computer terminal.

Some Basics

Integrated Circuits for TVT use

Memory

System Timing - Calculation and Circuits

Cursor and Update Circuits

Keyboards and Encoders

Serial Interfaces

Television Interfaces

Hard Copy and Color Graphics

This book guided many hobbyist and professionals in designing video displays for home computer systems. The cassette interface design from chapter 7 was the basis for the Kansas City standard. The circuits in this book did not rely on a microprocessor, just TTL. The TV Cheap Video Cookbook (1978) showed the TVT 6 5/8 that would work with a 6502 or 6800 microprocessor. The design was targeted at the KIM-1 Microcomputer.

The original TV Typewriter book cover shows an ASCII keyboard designed by Don Lancaster and sold by Southwest Technical Products. An early computer store chain, the Byte Shop, had the publisher add their logo to the covers and sold the TTL Cookbook and the TV Typewriter Cookbook in their stores. A later edition cover was designed for Radio Shack stores. The ninth printing of the first edition was in 1983.

^Freiberger, Paul; Swaine, Michael (2000). Fire in the Valley: The Making of the Personal Computer. New York: McGraw-Hill. pp. 35–36. ISBN0-07-135892-7. "A giant step toward the realization of the personal-computer dream happened in 1973, when Radio Electronics published an article by Don Lancaster that described a 'TV Typewriter'."

^Ceruzzi, Paul E. (2003). A History of Modern Computing. Cambridge, MA: MIT Press. p. 226. ISBN0-262-53203-4."One influential project was the TV-Typewriter, designed by Don Lancaster and published in Radio-Electronics in September 1973."